Sulfinate and Carbene Co-catalyzed Rauhut-Currier Reaction for Enantioselective Access to Azepino[1,2-a]indoles.

A carbene and sulfinate co-catalyzed intermolecular Rauhut-Currier reaction between enals and nitrovinyl indoles is disclosed. The carbene catalyst activates the enal and the sulfinate co-catalyst activates the nitrovinyl indole. Both activation processes are realized via the formation of covalent bonds between the catalysts and substrates to generate catalyst-bound intermediates. The dual catalytic reaction affords azepino[1,2-a]indole products with excellent stereoselectivity. Our study demonstrates the unique involvement of sulfinate as an effective nucleophilic catalyst in activating electron-deficient alkenes for asymmetric reactions. This dual catalytic approach should also encourage future explorations of both sulfinate and carbene catalysts for new reactions.